It is known that hydrazine compounds are added to silver halide photographic emulsions or developing solutions as disclosed in U.S. Pat. No. 3,730,727 (developing solutions containing ascorbic acid and a hydrazine compound in combination), U.S. Pat. No. 3,227,552 (the use of hydrazine compounds as auxiliary developing agents to obtain a direct positive color image), U.S. Pat. No. 3,386,831 (the use of .beta.-monophenyl hydrazides of aliphatic carboxylic acids as stabilizers for silver halide photographic materials), U.S. Pat. No. 2,419,975, Mees, The Theory of Photographic Process, third edition (1966), page 281, etc.
Among them, U.S. Pat. No. 2,419,975 discloses that a high-contrast negative image can be obtained by adding hydrazine compounds.
It is disclosed in U.S. Pat. No. 2,419,975 that very high contrast photographic characteristics of a gamma (.gamma.) value of higher than 10 can be obtained by adding hydrazine compounds to silver chlorobromide emulsions and carrying out development with developing solutions having a pH of as high as 12.8. However, strongly alkaline developing solutions having a pH of nearly 13 are likely to be oxidized by air. Hence such strongly alkaline developing solutions are unstable and can not be stored or used over a long period of time.
Attempts have been made to develop silver halide photographic materials with developing solutions having a lower pH to obtain a high-contrast image.
JP-A-1-179939 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") and JP-A-1-179940 (which correspond to U.S. Pat. No. 5,139,921) disclose a processing method wherein photographic materials containing nucleating development accelerators having an adsorptive group to silver halide grains and nucleating agents having an adsorptive group to the grains are developed with developing solutions having a pH of not higher than 11.0. However, when the amount of the compounds having an adsorptive group which is added to silver halide emulsions exceeds a critical amount, there are the disadvantages that light sensitivity is deteriorated, development is restrained and the effect of other useful adsorptive additive is deteriorated. Accordingly, the amount of the compounds having an adsorptive group must be limited to a certain amount, with the result that a sufficiently high contrast can not be obtained.
U.S. Pat. Nos. 4,998,604 and 4,994,365 disclose hydrazine compounds having an ethylene oxide repeating unit and hydrazine compounds having a pyridinium group. However, as can be seen in Examples in these U.S. patents high contrast degree is not sufficient, and it is difficult to obtain high contrast and a desired Dmax under practical development processing conditions.
Further, the photographic characteristics of nucleating high-contrast photographic materials greatly fluctuate with change in the pH of the developing solutions. The pH value of the developing solutions is greatly changed by the oxidation of the developing solutions by air and an increase in the concentration thereof caused by the evaporation of water or a lowering in the concentration thereof caused by the absorption of carbon dioxide in air. Accordingly, attempts have been made to reduce the dependence of the photographic performance on the pH of developing solutions.
As mentioned above, there is no conventional photographic material which provides sufficiently high contrast even though it is developed with a developing solution having a pH of not higher than 11 and which is scarcely dependent for its photographic performance on the pH of the developing solution.